Acoustic signaling system

• US 6,760,276 B1
• Filed: 02/11/2000
• Issued: 07/06/2004
• Est. Priority Date: 02/11/2000
• Status: Expired due to Fees

• Current Assignee: Gerald S. Karr
• Original Assignee: Gerald S. Karr
• Inventors: Karr, Gerald S.
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): NGUYEN, NAM V
• Application Number:
  US09/503,615
• Time in Patent Office: 1,607 Days
• Field of Search: 341/176, 348/734, 348/769, 345/158, 375/219, 375/287, 375/295, 375/316, 375/318, 704/205, 704/206, 704/210, 704/220, 704/224, 704/229, 704/240, 704/265, 704/216, 367/197, 367/198, 367/199, 340/952, 340/692
• US Class Current: 367/197
• CPC Class Codes: G08B 3/10 using electric transmission; using electromagnetic transmission
• CPC Class Codes: G10K 15/02 Synthesis of acoustic waves synthesis of speech G10L13/00

Abstract

An acoustic signaling system comprises a transmitter, which has frequency stability to create sounds which can reliably be received and which is loud enough to be heard by a receiver. The receiver includes an electret microphone, a limiting amplifier which has high gain, high frequency roll off and produces a maximum output for any input above a minimum value and a Schmitt trigger circuit to square up the output of the limiting amplifier and function as a zero cross detector. A micro-controller measures the times of the zero crossings and performs the detection and decoding algorithms to determine what code is being received. Each code consists of an anonymous repeating sequence of tones, which are transmitted for a certain duration followed by a silence, which allows room echoes to decay. The system creates acoustic sound codes, which are pleasant, sounding, can reliably be received and convey sufficient information to activate toys or dolls.

Claims

1. An acoustic signaling system comprising:

a transmitter for producing predetermined coded sound, the coding of said sound consisting of a continuously repeating pattern of different tones, each tone in the sequence being different in frequency from the tone immediately preceding it, and each tone consisting of a burst of that tone followed by a silence gap to permit echoes to decay, the purpose of said codes being to accurately transmit information from transmitter to receiver in a reasonably short period of time, and having the ability to successfully transmit said information to a receiver acoustically if the physical environment does or does not create reflections and echoes, and if the transmitter and receiver are, or are not, in motion relative to each other, and if the transmitter and receiver are close to or at a large distance from each other; and

a receiver responsive to the coded sound bursts including a micro-controller to activate various functions determined by successful reception of at least one complete sequence of the coded sound burst.

2. An acoustic signaling system in accordance with claim 1 wherein:

the transmitter comprises a computer to produce the pleasant sounding codes.

3. An acoustic signaling system in accordance with claim 2 wherein:

the receiver comprises;

an electret microphone for receiving transmitted acoustic output signals;

a limiting amplifier, coupled to the microphone, which provides a maximum output for any input signal thereto above a minimum value;

a Schmitt trigger circuit receiving and squaring up the output of the limiting amplifier; and

,

a micro-controller receiving the squared output of the trigger circuit to determine what code is being transmitted and perform functions determined by the code.

4. An acoustic signaling system in accordance with claim 1 wherein:

the transmitter comprises means for producing and sending said sound codes further including a speaker.

5. A method for acoustically signaling a receiver in accordance with claim 1 comprising the steps of:

transmitting predetermined coded sound bursts interrupted by gaps;

providing a receiver for the sound bursts including a micro-controller having control logic therein;

decoding the sound bursts in the micro-controller including

a) obtaining counts in clock cycles between adjacent zero crossings;

b) averaging two consecutive readings to obtain a value;

c) comparing each value with predetermined acceptable values;

d) sorting the input values into frequency bins;

e) adding a weighted factor to each matched frequency bin proportioned to the period of the bin to convert from a zero cross to an energy versus time representation, the factor being multiplied;

f) examining the energy inputs in the frequency bins to determine if any valid codes are being received; and

,

g) feeding an output signal to the control logic of the micro-controller if a valid code is received.

6. A method for acoustically signaling a receiver in accordance with claim 5 wherein:

the weighting to produce the weighted factor is proportional to the period of the input signal to the period of the input to the frequency bin.

7. A method for acoustically signaling a receiver in accordance with claim 5 wherein:

the examining of the energy in the frequency bins comprises;

a) maintaining a history of all frequency bins for shape discrimination;

b) convolve said history with a digital filter coefficients to produce a filtered output for the next step, one filter calculation of each bin, said coefficients resulting in the calculation of a low pass filter function with a cutoff frequency near the expected rate of change of tones in the transmitter;

c) comparing the outputs of the bin filters to determine if a tone as received is sufficiently dominant;

d) examining a history of previous valid tones to determine if a valid continuously repeating n-length code is being received and if the timing of appears to be valid; and

,

e) providing, if valid, an output to the control logic of the micro-controller.

8. A method for acoustically signaling a receiver in accordance with claim 7 further including the steps of:

requiring the successful reception of n+m continuously repeating tones in sequence for an n length code, m being greater than zero;

to increase the noise immunity thereof wherein the n-length code is repeated for a period of time longer than the time it takes to transmit the code (n+m)/n times, and said noise immunity increasing as m increases.

9. An acoustic signaling system in accordance with claim 1 wherein:

the coded sound bursts are anonymous sounding to a human listener wherein the code may begin on any of the constituent tones and end on any of the constituent tones provided the length of the transmitted sequence is sufficient for detection.

10. An acoustic signaling system in accordance with claim 1 wherein:

the transmitter comprises user controls coupled to a microprocessor to provide a predetermined output, a digital to analog converter receiving said output, an amplifier coupled to the digital to analog converter and a speaker receiving the amplifier output to provide the desired acoustic signals.

11. An acoustic signaling system in accordance with claim 1 wherein:

the transmitter comprises a transmitter device such as a cassette player or a VCR connected to a TV for acoustic output.

12. An acoustic signaling system in accordance with claim 1 wherein:

the transmitter comprises a broadcast station and a corresponding standard receiving device such as a radio or TV, the sound output of said receiving device serving as an acoustic transmitter for the signaling purposes.

13. An acoustic signaling system in accordance with claim 1 wherein:

the receiver comprises a microphone for receiving transmitted acoustic signals and a personal computer connected thereto to receive said signals, said computer including a PC sound card, a disk for loading a program into the computer and a main CPU for receiving signals from the sound card and performing algorithms in accordance with the disk program determined by the signals.

14. An acoustic signaling system in accordance with claim 1 wherein:

the receiver comprises an electret microphone for receiving transmitted signals and a Palm Pilot™

or other computing device connected thereto, said Palm Pilot™

or other computing device including software to perform the actions necessary to implement the invention described in claim 1.

15. An acoustic signaling system in accordance with claim 1 wherein:

the coded sound bursts comprise a plurality of code subsets wherein each subset of the available codes in comparison to another subset is unidentifiable to a human listener.

16. An acoustic signaling system in accordance with claim 1 wherein:

the coded sound bursts are within the audible hearing range but are unidentifiable and anonymous to a human listener.

17. An acoustic signaling system in accordance with claim 1 wherein:

the receiver dynamically adjusts the validity and time models for the received codes based on the quality level of the data received, so that if the shape of the filtered tone bins over time does not match the preferred shape, the microcontroller can check to see if the shape of the filtered tone bins over time matches a secondary or tertiary timing model, to determine if the transmitter has switched to a slower or faster tone pulse rate, and if one of the alternate shapes is matched the microcontroller can output the corresponding data signal.

18. An acoustic signaling system in accordance with claim 1 wherein:

the sound bursts each comprise a plurality of p tones and wherein

the transmitter may start a sound burst comprising a code on any of the p tones and stop each code on any one of the p tones.

19. An acoustic signaling system in accordance with claim 1 wherein:

the transmitter comprises multiple channels, each channel defined as an unique tone subset of the set of p tones.

20. An acoustic signaling system in accordance with claim 1 wherein:

the receiver comprises multiple receivers to receive the transmitted sound codes.

21. An acoustic signaling system in accordance with claim 1 wherein:

the receiver is responsive to a valid audio sound code which is received and followed within a predetermined time interval by another valid audio sound code, the two or more sound codes together may be interpreted as individual digits of a larger set of codes, the base of the larger set being determined by the number codes available in the small set.

22. An acoustic signaling system in accordance with claim 1 wherein:

selected timing parameters are provided to slow down the time in cases of extreme echo.

23. An acoustic signaling system in accordance with claim 1 wherein:

the transmitter comprises means for producing and sending coded tone sequences interrupted by gaps, said sound being generated by mechanical means, i.e. a whistle with mechanically changing tuning, combined with a mechanical cam or other mechanical arrangement to select the proper tones in the proper sequence.

24. An acoustic signaling system in accordance with claim 1 wherein:

the purpose of said codes being to accurately transmit information from transmitter to receiver in a reasonably short period of time on the order of one second or less.

25. An acoustic signaling system comprising:

a transmitter for producing predetermined coded sound, the coding of said sound consisting of a continuously repeating pattern of different tones, each tone in the sequence being different in frequency from the tone immediately preceding it, and each tone consisting of a burst of that tone followed by a silence gap to permit echoes to decay, the purpose of said codes being to accurately transmit information from transmitter to receiver in a reasonably short period of time and having the ability to successfully transmit said information to a receiver acoustically if the physical environment does or does not create reflections and echoes, and if the transmitter and receiver are, or are not, in motion relative to each other, and if the transmitter and receiver are close to or at a large distance from each other;

the transmitter comprises a computer to produce the pleasant sounding codes;

a receiver responsive to the coded sound bursts including a micro-controller to activate various functions determined by successful reception of at least one complete sequence of the coded sound burst, wherein,

the receiver comprises;

an electret microphone for receiving transmitted acoustic output signals;

a limiting amplifier, coupled to the microphone, which provides a maximum output for any input signal thereto above a minimum value;

a Schmitt trigger circuit receiving and squaring up the output of the limiting amplifier; and

,

a micro-controller receiving the squared output of the trigger circuit to determine what code is being transmitted and perform functions determined by the code.

26. A method for acoustically signaling a receiver comprising the steps of:

transmitting predetermined coded sound bursts interrupted by gaps;

providing a receiver for the sound bursts including a micro-controller having control logic therein;

decoding the sound bursts in the micro-controller including

a) obtaining counts in clock cycles between adjacent zero crossings;

b) averaging two consecutive readings to obtain a value;

c) comparing each value with predetermined acceptable values;

d) sorting the input values into frequency bins;

e) adding a weighted factor to each matched frequency bin proportioned to the period of the bin to convert from a zero cross to an energy versus time representation, the factor being multiplied;

f) examining the energy inputs in the frequency bins to determine if any valid codes are being received;

g) feeding an output signal to the control logic of the micro-controller if a valid code is received;

the examining of the energy in the frequency bins comprises;

a) maintaining a history of all frequency bins for shape discrimination;

b) convolve said history with a digital filter coefficients to produce a filtered output for the next step, one filter calculation of each bin, said coefficients resulting in the calculation of a low pass filter function with a cutoff frequency near the expected rate of change of tones in the transmitter;

c) comparing the outputs of the bin filters to determine if a tone as received is sufficiently dominant;

d) examining a history of previous valid tones to determine if a valid continuously repeating n-length code is being received and if the timing of appears to be valid;

e) providing, if valid, an output to the control logic of the micro-controller;

requiring the successful reception of n+m continuously repeating tones in sequence for an n length code, m being greater than zero; and

to increase the noise immunity thereof wherein the n-length code is repeated for a period of time longer than the time it takes to transmit the code (n+m)/n times, and said noise immunity increasing as m increases.